Such flexible line elements are generally inserted in lines as intermediate pieces or adaptors in order to absorb movements and oscillations and bring about decoupling from the passing on to adjacent components. These elements are particularly used in lines carrying hot gases. Temperature change-caused length variations occur, so that these line elements must have a high flexibility and a large tolerance with respect to radial and axial movements.
In order to meet these requirements the bellows forming the gastight connection must have a correspondingly thin-walled construction. However, against this is set the requirement that in the case of hot gas flows the bellows must have an adequate thermal and compression loadability. Thus, the bellows must be dimensioned in such a way that a compromise is found between a good mobility and an adequate thermal and compression loadability. A temperature reduction for decreasing the embrittlement risk is particularly important with nickel-based materials. It has already been proposed to arrange a fibrous layer within the bellows and to force it into the bellows corrugations by stuffing. This leads to a complicated construction, which makes necessary a clasp hose for retaining the insulating material and it is difficult to obtain an adequate thermal insulation.
A device of the aforementioned type is known from GB-A-2 052 665. The latter has a movable tubular connection with a bellows in the form of a shaft. Within the bellows is provided a corrugated insulating hose, whose ends are in each case arranged jointly with the bellows on the connecting pieces. The insulating hose comprises an insulating material layer placed between two textile layers.
It is disadvantageous that in the fixing area at the ends of the insulation, the insulating material is highly compressed by fixing to the bellows and at this point passes a large amount of heat to the bellows. A corrugated insulation cannot be made very thick for deformation reasons, even if this was necessary. The manufacture of the corrugated insulation is complicated and expensive. The corrugated insulation fixed at both sides increases the stiffness of the compensator (increased adjusting forces). A 100% gastight binding of the bellows to the connecting pieces is problematical in conjunction with the interposed insulation. The corrugated insulation has a finite life, because it moves with the bellows.
U.S. Pat. No. 2,937,036 discloses a thermostable pipe coupling between two pipe ends. The pipe ends form an inner telescopic connection and are surrounded by an outer telescopic connection. This comprises outer, telescoped pipe sections, which are arranged by means of ribbed heat radiating elements on in each case one pipe end and have in their insertion area an interposed O-ring for sealing purposes. A glass fibre mat is arranged for thermal insulation purposes between the outer and inner telescopic connection.
The known device has a bellows for the flexible, gastight connection of the pipe ends. The displaceable O-ring used is not absolutely gastight. The thermal insulation is neither placed in the interior, nor is a fixed insulating cassette provided. As the thermal insulation is not in the interior, there is a contact of outer pipe sections with pipe areas, which on the inside are directly subject to the action of a possibly hot medium, so that heat radiating elements are additionally required for insulation. In addition, the device comprises a plurality of parts and is complicated to manufacture.